Submitted to: Journal of Dairy Science
Publication Type: Abstract Only
Publication Acceptance Date: 2/28/2005
Publication Date: 7/24/2005
Citation: Norman, H.D., Wright, J.R., Powell, R.L., Van Raden, P.M., Miglior, F. 2005. Comparison of maturity rate for bull daughters in the United States and Canada [abstract]. Journal of Dairy Science. 88(Suppl. 1):10-11. Interpretive Summary:
Technical Abstract: Maturity rate of bull daughters in the United States and Canada were compared based on parity-specific predicted transmitting abilities (PTA) of sires. For US daughters, 305-d milk records for Holsteins with first-parity calving dates between 1960 and 1998 were used to calculate sire PTA based on first-parity daughter records (PTA1), first- and second-parity daughter records (PTA1-2), and first- through third-parity daughter records (PTA1-3). Sire evaluations with contributions only from second- (PTA2) or third-parity (PTA3) daughter records were approximated by weighting based on numbers of daughters with first, second, and third parities. For Canadian daughters, parity-specific estimated breeding values (EBV1, EBV2, and EBV3) of sires were those derived for November 2004 national evaluations. Correlations among parity-specific sire evaluations were calculated within birth year of bulls. Correlations for bulls with >=500 daughters in both countries were 0.87 between PTA1 and PTA2, 0.86 between PTA1 and PTA3, and 0.97 between PTA2 and PTA3 for US daughters; corresponding correlations were 0.90, 0.88, and 0.98 for Canadian daughters. Correlations between PTA2 - PTA1 and EBV2 - EBV1 were 0.63 for bulls with >=20 daughters, 0.82 for bulls with >=100 daughters, and 0.89 for bulls with >=500 daughters in both countries; corresponding correlations were 0.54, 0.76, and 0.85 for differences between third- and first-parity sire evaluations. Corresponding correlations for differences between third- and second-parity sire evaluations were considerably lower at 0.14, 0.27, and 0.52, probably because differences between second- and third-parity evaluations were small. Differences in maturity rate of bull daughters were reasonably consistent across countries. Modeling genetic evaluations to account for those differences would increase accuracy for bulls with daughters that deviate substantially from population mean.